Inside the Centre: The Life of J Robert OppenheimerBy Ray Monk (Jonathan Cape 832pp £30)

Oppenheimer: under a cloud

Describing his reaction to the testing of the atomic bomb in New Mexico on 16 July 1945, Robert Oppenheimer recalled:

We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture the Bhagavad Gita: Vishnu is trying to persuade the prince that he should do his duty and, to impress him, takes on his multi-armed form and says: 'Now I am become death, the destroyer of worlds.' I suppose we all thought that, one way or other.

Recorded for a film documentary twenty years after the event, Oppenheimer's account of the test was to become a canonical expression of contemporary angst. Yet it hardly squares with the reports of others who were present at the time. A military officer reported that Oppenheimer's face 'relaxed into an expression of tremendous relief' at the moment the explosion occurred. Far from being silent, the scientists queued up to howl triumphantly into the PA system. As one of them commented: 'Some people claim to have wondered at the time about the future of mankind. I didn't. We were at war and the damned thing worked.' If there was a sense of foreboding, it came only some time later.

Oppenheimer's account was a legend, one of many he devised throughout his life. In the view of Isidor Rabi, a lifelong friend, he was 'a man who was put together of many bright shining splinters', who 'lived a charade'. The charade, which involved denying or downplaying his Jewishness, prevented him developing a genuine personality of his own. By effacing his Jewish heritage Oppenheimer hoped to acquire an identity that was more socially acceptable. Given the anti-Semitism that was prevalent in America during much of his lifetime, it may not have been an unreasonable aspiration, but for Oppenheimer the result was to leave him with no identity at all.

Practically everyone who has written about Oppenheimer has noted his elusiveness, but until now no one has convincingly explained how he came to be this way. As Ray Monk shows in this superb new life, one reason is to be found in Oppenheimer's schooling. Born in 1904, he began attending the Ethical Culture School on Central Park West in New York in 1911. His father - an immigrant from Germany who would make his fortune in the textile trade - married Ella Friedman, a painter who had taught art at Barnard College, in a service conducted by Felix Adler, the founder of the Ethical Culture Society, of which the school was an offshoot. In some ways the Society shaped the course of Oppenheimer's life. Claiming to derive its precepts from Judaism but in fact promoting a secular version of Kant's idea of moral law, Adler's humanist creed was a formative influence on Oppenheimer. Insisting that the moral life had to be severed from religion, it shut him off from the spiritual traditions of Judaism. At the same it promoted the development of 'spiritual personality', a nebulous ideal that left Oppenheimer unsatisfied. Learning Sanskrit in the 1930s in order to read the Hindu scriptures in the original, he embarked on an enduring but ultimately unrewarding engagement with mysticism.

A philosopher who has produced impressive lives of Wittgenstein and Russell, Monk gives an illuminating analysis of Oppenheimer's part in what the Nobel Laureate Steven Weinberg described as 'the most profound revolution in physical theory since the birth of modern physics in the seventeenth century'. During the 1920s, when Oppenheimer was at the start of his career, the mechanistic model inherited from classical physics was being challenged by one that recognised uncertainty as an integral feature of the world. He went on to make notable contributions to theoretical physics, but the indeterminacy in the nature of things theorised in the new physics was also a feature of Oppenheimer's personality, and more than anything else it was this that brought his career to an end.

Countless pages have been written on whether he was a genuine security risk or simply a casualty of McCarthyism and the jealousy of some of his colleagues. There has never been any evidence to support the accusation - made by some of his enemies and detractors when he was hauled to Washington for an inquisition by the House Un-American Activities Committee in 1949 - that he was recruited as a Soviet agent. Whether he was a communist is not so easily decided. As Monk puts it:

The question of whether Oppenheimer was a communist is rather like the question of whether he was or was not a German Jew. He did not consider himself to be German, Jewish or communist, and yet, as these words are commonly used, he was ethnically a German Jew and politically a communist.

In operational terms, there can be no doubt that Oppenheimer was a communist. He may not have had a party card, but neither did many of those working actively for the communist cause at the time. As Monk acknowledges, he was a member of a covert communist group set up at Berkeley and, according to the few who were aware of his involvement, he certainly regarded himself as a communist at the time. Yet he never admitted that he belonged in the group, or even hinted at its existence. When questioned by American security officers in 1943, he pointed the finger at colleagues he believed were willing to pass on sensitive information to the Soviets. In doing so he incriminated himself, since the extent of his knowledge gave the impression that he too might be involved in espionage. There was no factual basis for this perception, but by trying to deflect suspicion onto others he placed a question mark over himself and those closely associated with him. As Monk writes: 'What he had done was sow the seeds of his own downfall and that of many of his friends, students and colleagues.'

The question remains why Oppenheimer acted as he did. One reason was given by Einstein, a much stronger and shrewder man: 'The trouble with Oppenheimer is that he loves a woman who doesn't love him - the United States government.' Oppenheimer wanted desperately to be an inside man - someone consulted and trusted by the American authorities. That is why he was ready to cast aside his communist past when his loyalties came into question. The result was to leave him more of an outsider than ever.

Towards the end of his life Oppenheimer turned against the Bhagavad Gita's philosophy of detachment, which had consoled him for so many years. 'If I cannot be comforted by Vishnu's argument to Arjuna,' he declared in a speech to the Congress of Cultural Freedom, 'it is because I am too much of a Jew, much too much a Christian, far too much an American. For I believe in the meaningfulness of human history, and of our role in it, and above all of our responsibility to it.' In effect, he was reaffirming the humanist creed he had imbibed at the Ethical Culture School. But it was the lack of substance of that creed that had led him to mysticism, and when he renounced detachment he must have known he had by then forfeited any chance of meaningful action. Ray Monk concludes by observing that 'the feebleness in Oppenheimer of the "element of earthiness", the sense one has of him being almost disembodied', helped make him 'the great man he showed himself to be'. But if the person that emerges from this magisterial and moving book was great, it was only in contending with great events. In himself he was a lost soul, a man of prodigious and many-sided intelligence who could not find a place in the world.